Gold-extracting process.



UNITED STATES Patented June 30, I903.

PATENT OFFICE GOLD-EXTRACTINTG- PROCESS.

SPECIFICATION forming part of Letters Patent No. 732,639, dated June 30,1903.

Application filed June 21,1902. Serial No. 112,562. ,(No specimens.)

To all whom, it may concern:

Be it known that I, THOMAS E. JOSEPH, a citizen of the United States,residing at Mercur, in the county of Tooele and State of Utah, haveinvented certain new and useful Improvements in Gold-ExtractingProcesses; and I do declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same. v

My invention relates to the extraction of precious metals, but moreparticularly to gold, and has for its object to extract gold from orecontaining the same when in a suitable condition.

A further object of my invention is to provide a process for extractingprecious metals which can be used on base, oxidized, or mixed ore, andwhich will not be neutralized by the presence of arsenic or sulfur, andwhichflwill leach both roasted and unroasted ores;

It must be understood that I cannot state definitely'how fine the oreshould be crushed, as loose-sand ore should be leached in itsnaturalstate, while soft ore should notbe crushed as fine as hard orbase ores, the fineness of crushing depending entirely upon the quality,

impenetrability, and hardness of the ore to be leached. I

In carrying out my invention after the ore has been crushed, asaforesaid, I subject the same to the leaching solution composed ofwater, cyanid of potassium, bromin, hydrate of calcium, peroxid ofbarium, and carbon dioxid, in conjunction with compressed air conveyedupward therein through the bottom from an air-compressor.

In carrying out my process such vessels as have been found to be mostpractical in the extracting of gold are'used, although I prefer thosemade of wood, as metal will be more or less subject to the chemicalaction of the leaching solution, and I prefer to have the storagetankstanding at one side at a higher elevation than the ore-leaching tank,so that the leaching solution will run by the force of gravity into thetank containing the ore. The leaching solution, composed of water,cyanid of potassium, bromin, peroxid of barium, and hydrate of calcium,is prepared in the storage-tank, and when carbon dioxid isdeleaching-tank or in the storage-tank, as desired, or it may beobtained from well-burned .from bya pipe either into the solution in theI coal-smoke after the sulfur has been extracted from the smoke, or itmight be obtained by using carbonated water, such as is used atsoda-fountains, and it be conveyed into the leaching solution in likemanner as above described.

The compressed air is conveyed into the tank of ore being leached in anyapproved manner for the purpose of agitating the ore as well as to helpto convey the slimes, if any therein, toward the top, in order toaidIt-he percolation of the solution through the ore and to neutralizethe sulfur in the ore. Great care must be taken, however, not to admitthe air under too-great pressure, as channeling might result, whichwould retard the leaching of the ore. Therefore compressed air should beturned on slowly and gradually increased to the desired amount. Thecarbon dioxid in the'solution, moreover, neutralizes to some extent thealkalinity of the solution and helps to neutralize any sulfur on theore, which would otherwise be injurious in a cyanid-of-potassiumsolution by tending to retain or precipitate the precious metals backinto the tailings. The carbon dioxid also helps to more dissolve thehydrate of lime therein, and thereby more quickly conveys the same intothe ore as soon asthe solution can penetrate it to there form aninsoluble compound composed of the lime hy-' drate and the sulfur orarsenic in either the ore or the solution, thereby preventing theirinjury to the cyanid solution and the cyanids of the precious metals.v

Bromin in the solution will at once attack the cyanid of potassium andliberate the nascent oyanogen and form the cyanogen bromid therewith. Ifthere were no free oxygen in the solution, a part of the bromin wouldcombine with the potassium of the cyanid of potassium and form bromid ofpotassium; but free oxygen liberated from peroxid of barium in thesolution by the water and from compressed air will again liberate thebromin from the bromid of potassium, which freed bromin will then joinwith the free cyanogen and form more cyanogen bromid. I might use thesolid bromid; but I prefer to use the bromin in the liquid form and inabout the proportion of one ounce to each ton of the solution, althoughI do not confine myself to any particular proportion, as some ores willrequire a larger or less amount of bromin, and also vary the proportionsof the other chemicals in the solution.

As it is expedient to have free potassium cyanid present with thecyanogen bromid, it is advisable to remove the cyanid-destroyingcompounds either by washing with water before the leaching is commencedor else to use carbon dioxid, hydrate of calcium, peroxid of barium, andcompressed air therein to neutralize the cyanid-destroying compounds.

Cyanogen bromid has far greater activity and power as a solvent toextract precious metals from the ore in the presence of free oxygen andhydrate of calcium in the alkaline solution than cyanogen has. If thereis an excess of bromin present, then paracyanogen is formed; butexperiments show that a weak solution of bromin is the most efficient.

It will be observed that while a very weak amount of carbon dioxid inwater will precipitate calcium, yet a larger amount of carbon dioxidtherein will dissolve calcium hydrate of the milk of lime the more andhelp to clarify the solution. I have found that carbon dioxid in thissolution is ofmuch more value in this connection than the bicarbou atesof potassium, sodium, or ammonium, for the reason that too much of thealkalids of those metals would be injurious, because they would tend todissolve base metals into the solution and foul it if the solutionbecame too alkaline, as the ores are often quite alkaline.

In ores rich in sulfur, tellurium, antimony, bismuth, realgar, ororpiment I prefer to first extract the most of these elements by anotherleaching process of my own and then to afterward extract the preciousmetals, as herein stated; also, by reason of using this weaker solutionof cyanid of potassium rather than the heretofore practice and theconsequent weaker alkalinity therein then not so much of the zinc andiron would be dissolved therein to foul the solution, as was often thecase heretofore with too strong an alkaline solution.

When it is desired to hasten the process of leaching or to prevent thesolution from freezing in winter, the compressed air may be heated by aheating-furnace through which a coil of the air-pipe passes.

The oxygen liberated in the solution from vsaese peroxid of barium addedtherein, as well as the oxygen from the compressed air, will not onlyliberate the nascent cyanogen quickly, but they both will also furnishplenty of oxygen to assist the nascent cyanogen and the cyanogen bromidin their work, as well as to help to neutralize the injurious effects ofsulfur in the ores, thereby facilitating the better extraction of goldfrom arsenical and sulfurous ores by the nascent cyanogen and cyanogenbromid in the alkaline solution Were it not for the hydrate of calcium,peroxid of barium, compressed air, and the cyanogen bromid in thesolution some of the said ores would have to be roasted, thus making theprocess much more expensive, and consequently detracting from the valueof the ores.

I Wish to be understood as distinguishing between the use of hydrate ofcalcium and oxid of lime and lay no claim to the latter, for the reasonthat the dissolving of the same into the hydrate of calcium in theleaching liquor is so slow that the sulfur and arsenic in the ore willhave injured the cyanid of potassium and eyanids of the precious metalsbefore the oxid of lime is dissolved, thus rendering its use of littleor no benefit to neutralize the sulfur and arsenic until after the saidacids have done their harmful work. Hydrate of calcium, however, isthoroughly mixed with the leaching liquor before the same has been runin the ore, either upwardly or downwardly, to be leached. Hydrate ofcalcium, compressed air, peroxid of barium, and carbon dioxid in thesolution immediately neutralize the most of the baseness or refractorynature of the ore, as lime would form an insoluble compound with thearsenic, while barium and sulfur would form the insoluble compoundofbarium sulfate, and the thus liberated oxygen from the barium peroxidwould greatly aid the extraction of the precious metals.

The oxygen libe rated from barium peroxid by the water also causes thepyrites to be oxidized to sulfate of iron and the gold to be set atliberty from the pyrites, which thereby eauses the better extraction ofthe gold. The normal oxid of barium which is left after the above workis performed then decomposes the sulfate of iron in the solution,forming sulfate of barium and oxid of iron, both of which are insoluble.It also removes sulfur from the sulfocyanids and dispenses with the useof much of the lime oxid as heretofore has been customary to use. Thereshould be more peroxid of barium added on pyritic or sulfurous than onfree-milling ore.

As a general rule there should be about two and one-half pounds ofcyanid of potassium added in each ton of water for the solution, thoughoftentimes a stronger or Weaker solution will be found beneficial, ascircumstances may require.

The addition thereto of the bromin, carbon dioxid, hydrate of calcium,peroxid of barium, and compressed air assists the leaching to IIO drateof calcium to each ton of the solution v in addition to any dust of oxidof' limethat might be added or scattered into the ore when the latter isdumped into the tank to be leached to sweeten the same to prevent anybad odor that might afterward occur when emptying out the tailings.

There should be about one-half of a pound of peroxid of barium added toeach ton ofwater for the solution for the average ore; but some orescontaining more sulfur would require a larger amount to neutralize thesulfur in the ore, while some free-milling ore would do with a lessamount of peroxid of barium.

After the ore is leached the solution is drained off into another tank,from whence it may be drained through boxes containing zinc-shavings orcharcoal, or both, for the precious metals to be precipitated thereon,or the precious metals may be precipitated from the solution byelectricity or with zinc-dust stirred therein, though I prefer to usezincdust. The leaching liquor can then be pumped from there, or from asump-tank when run into it or from the gold-solution tank without anyprecipitation of its metals, back to the storage-tank, ifdesired, tothere be replenished to the desired quantity and strength in order touse again to leach same or other ore.

When desiring to finish up a tank of leaching ore, a wash-Water shouldbe run through it to wash out as much as is convenient of the remainingcyanide of the precious metals as may have remained therein and be savedto again use as a wash-water or to replenish:

the quantity of the strong solution. In this way the wash-water may beused over and over again as often as desired, the pipes connecting thedifierent tanks and pumps being provided with stop-cocks, 'so as tocontrol and regulate the flow of the leaching liquor and also thecompressed air.

I lay no claim to the apparatus,- nor do I claim,broadly, the use ofcompressed air nor any particular mode of precipitation of the preciousmetals, nor do I wish to be understood as claiming an alkaline earth inthe solution-as potassium, sodium, or ammonium-but confine myself tohydrate of calci um, for the reason the aforementioned earths beingalkaline are injurious, especially as they help to dissolve base metalsin the solution, and thereby to foul it, while the hydrate of calciumand peroxid of barium neutralize the base acids of sulfur and arsenic,if any therein, and thus prevent the sulfur and arsenic from fouling thesolution and also prevent the ore acids of sulfur and arsenic fromattacking the cyanids of the precious metals and precipitating them backinto .the tail- 1ngs.

What I claimtas new, however, and desire to secure by Letters Patent ofthe United States, is-

1. The herein-described process of extracting gold and silver from orecontaining the same, when in a suitable condition,which consists insubjecting the said ore to the leachingaction of a solution containingwater, cyanid of potassium, bromin, hydrate of,calcium, peroxid ofbarium and carbon dioxid, and simultaneously agitating the ore, bycompressed air being forced upward through the same, substantially asdescribed.

2. The hereindescribed process of extracting gold and silver from orecontaining the same, when in a suitable condition, which consists insubjecting said ore to a leaching acperoxid of barium and carbon dioxid,said carbon dioxid being forced into the leachingsoluti0n',simultaneously with compressed air, as andfor the purpose setforth.

3. The herein-described process of extracting gold and silver from orecontaining-the same when in a suitable condition, which consists insubjecting the said ore to the leach potassium, bromin, hydrate ofcalcium, and

peroxid of barium.

5. The herein-described process of extracting gold and silver from orecontaining-the same, when in suitable condition, which con-- sists insubjecting the said ore to the leaching action of a solution containingwater, cyanid of potassium, bromid and peroxid of barium.

In testimony whereof I affix my signature in presence of two witnesses.

Witnesses:

ELLA PATTEN, CHRIssIE JOHNSON;

THOMAS B. JOSEPH.

